Ramadan fasting starts when the crescent is seen and it is finished when the new crescent is seen. According to majority of schools of law when the moon is seen anywhere in the world all Muslims have to start observing the fasting. However, the shafii school of law argues that the moon needs to be seen locally. The other issue is related to the seeing the moon. Some hold that astronomy and its prediction is valid while others insist that the moon has to be seen by naked eye. These types of issues cause disputes and disagreements among Muslims. This year I started observing fasting at June 6, so I would recommend you do the same.